# Redis Enterprise Software release notes 6.4.2-81 (June 2023)

```json metadata
{
  "schema_version": 2,
  "title": "Redis Enterprise Software release notes 6.4.2-81 (June 2023)",
  "description": "Email alerts for database backup failures and replica high availability shard relocation failures.",
  "categories": ["docs","operate","rs"],
  "tableOfContents": {"sections":[{"id":"new-features-and-enhancements","title":"New features and enhancements"},{"id":"resolved-issues","title":"Resolved issues"},{"children":[{"id":"feature-limitations","title":"Feature limitations"},{"id":"operating-system-limitations","title":"Operating system limitations"}],"id":"known-limitations","title":"Known limitations"}]}

,
  "codeExamples": []
}
```


This is a maintenance release for ​[​Redis Enterprise Software version 6.4.2](https://redis.io/downloads/#software).

The following table shows the MD5 checksums for the available packages:

| Package | MD5 checksum (6.4.2-81 June release) |
|---------|---------------------------------------|
| Ubuntu 16 | 31631248672de0154ec20aee0bff9adc |
| Ubuntu 18 | eb4e8c1bc1443923ebcd457e51684f7e |
| Ubuntu 20 | 1256292b8dca6456e69dc309be51a8d0 |
| RedHat Enterprise Linux (RHEL) 7<br/>Oracle Enterprise Linux (OL) 7 | 1e51c5fdf22c0b6988565444ba08c6cd |
| RedHat Enterprise Linux (RHEL) 8<br/>Oracle Enterprise Linux (OL) 8 <br/>Rocky Enterprise Linux | 96dc036339fe18fb218e8d4c8ff50c99 |
| Amazon Linux 2 | 1a549bdb360c9e22ef764faeadbd4c90 |

## New features and enhancements

- RS77279 - Database backup failures and replica high availability ([replica HA](https://redis.io/docs/latest/operate/rs/databases/configure/replica-ha)) failures (for example, when relocating a shard from a node) now generate email alerts

#### Redis Stack v6.2.6

Redis Enterprise Software v6.4.2 includes the new features delivered in the latest [Redis Stack release (6.2.6 v6)](https://redis.com/blog/introducing-redis-stack-6-2-6-and-7-0-6/):

- [RediSearch v2.6.9](https://redis.io/docs/latest/operate/oss_and_stack/stack-with-enterprise/search)

- [RedisJSON v2.4.7](https://redis.io/docs/latest/operate/oss_and_stack/stack-with-enterprise/json)

- [RedisBloom v2.4.5](https://redis.io/docs/latest/operate/oss_and_stack/stack-with-enterprise/bloom)

- [RedisGraph v2.10.9](https://redis.io/docs/latest/operate/oss_and_stack/stack-with-enterprise/deprecated-features/graph)

- [RedisTimeSeries v1.8.10](https://redis.io/docs/latest/operate/oss_and_stack/stack-with-enterprise/timeseries)

See [Upgrade modules](https://redis.io/docs/latest/operate/rs/installing-upgrading/modules/upgrade-module) to learn how to upgrade a module for a database.

## Resolved issues

- RS101204 - Fixed high memory consumption that was caused by the `persistence_mgr` service when AOF persistence is configured for every second.

- RS39322 , RS35526  - [`rlcheck`](https://redis.io/docs/latest/operate/rs/references/cli-utilities/rlcheck) no longer requires root privileges and can run with the `redislabs` group and user.

- RS97315, RS100853  - Fixed the robustness of the support package process when collecting the shard configuration.

- RS65110 - Fixed firewalld SELinux configuration.

- RS101691 - Clean false error messages at the end of installation. 

## Known limitations

### Feature limitations

- RS78430 - When [tuning module arguments](https://redis.io/docs/latest/operate/rs/references/cli-utilities/rladmin/tune#tune-db), typos or unsupported arguments can cause shards to get stuck after restarting.

- RS40641 - API requests are redirected to an internal IP in case the request arrives from a node which is not the master. To avoid this issue, use [`rladmin cluster config`](https://redis.io/docs/latest/operate/rs/references/cli-utilities/rladmin/cluster/config) to configure `handle_redirects` or `handle_metrics_redirects`.

### Operating system limitations

#### Ubuntu 20.04

By default, you cannot use the SHA1 hash algorithm ([OpenSSL’s default security level is set to 2](https://manpages.ubuntu.com/manpages/focal/man3/SSL_CTX_set_security_level.3ssl.html#notes)). The operating system will reject SHA1 certificates even if the `mtls_allow_weak_hashing` option is enabled. You need to replace SHA1 certificates with newer certificates that use SHA-256. Note that the certificates provided with Redis Enterprise Software use SHA-256.